1. Technical Field
The present invention relates generally to a series of novel derivatives of 6,7-dihydro-5H-imidazo[1,2-a]imidazole-3-carboxylic acid amides, the synthesis of these compounds their use in the treatment of inflammatory disease and pharmaceutical compositions comprising these compounds.
2. Background Information
Research spanning the last decade has helped to elucidate the molecular events attending cell-cell interactions in the body, especially those events involved in the movement and activation of cells in the immune system (see generally, von Andrian U H, et al. N Engl J Med 2000; 343(14):1020-1034). Cell surface proteins, and especially the Intercellular Cellular Adhesion Molecules (“ICAMs”) and “Leukointegrins”, including LFA-1, MAC-1 and p150,95 (referred to in WHO nomenclature as CD18/CD11a, CD18/CD11b, and CD18/CD11c, respectively) have correspondingly been the subject of pharmaceutical research and development having as its goal the intervention in the processes of leukocyte extravasation to sites of injury and leukocyte movement to distinct targets. For example, it is presently accepted that prior to the leukocyte extravasation, which is a mandatory component of the inflammatory response, activation of integrins constitutively expressed on leukocytes occurs and is followed by a tight ligand/receptor interaction between integrins (e.g., LFA-1) and one or several distinct intercellular adhesion molecules (ICAMs) designated ICAM-1, ICAM-2 or ICAM-3 which are expressed on blood vessel endothelial cell surfaces and on other leukocytes. The interaction of the ICAMs with the Leukointegrins is a vital step in the normal functioning of the immune system. Immune processes such as antigen presentation, T-cell mediated cytotoxicity and leukocyte extravasation all require cellular adhesion mediated by ICAMs interacting with the Leukointegrins. See generally Kishimoto, T. K.; Rothlein; R. R. Adv. Pharmacol. 1994, 25, 117-138 and Diamond, M.; Springer, T. Current Biology, 1994, 4, 506-532.
A group of individuals has been identified which lack the appropriate expression of Leukointegrins, a condition termed “Leukocyte Adhesion Deficiency I” (Anderson, D. C.; et al., Fed. Proc. 1985, 44, 2671-2677 and Anderson, D. C.; et al., J. Infect. Dis. 1985, 152, 668-689). These individuals are unable to mount a normal inflammatory and/or immune response(s) due to an inability of their cells to adhere to cellular substrates. These data show that immune reactions are mitigated when lymphocytes are unable to adhere in a normal fashion due to the lack of functional adhesion molecules of the CD18 family. By virtue of the fact that LAD patients who lack CD18 cannot mount an inflammatory response, it was believed that antagonism of CD18/CD11/ICAM interactions will also inhibit an inflammatory response. The role of LFA-1 in immune cell trafficking and activation is well established and supported by studies with LFA-1 deficient mice and blocking anti-LFA-1 antibodies. In vitro, LFA-1 deficient lymphocytes are characterized by defects in aggregation and proliferation. In vivo parallel deficits in delayed type hypersensitivity (DTH) responses are observed. In animal models of organ transplantation, anti-LFA-1 antibodies have shown efficacy. Taken together these studies provide support for the role of LFA-1 in initiating and/or propagating inflammatory responses (Giblin, P. A. et al. Curr. Pharm. Design, 2006, 12: 2771-2795).
It has been demonstrated that the antagonism of the interaction between the ICAMs and the Leukointegrins can be realized by agents directed against either component. Specifically, blocking of the CAMs, such as for example ICAM-1, or the Leukointegrins, such as for example LFA-1, by antibodies directed against either or both of these molecules effectively inhibits inflammatory responses. In vitro models of inflammation and immune response inhibited by antibodies to ICAMs or Leukointegrins include antigen or mitogen-induced lymphocyte proliferation, homotypic aggregation of lymphocytes, T-cell mediated cytolysis and antigen-specific induced tolerance. The relevance of the in vitro studies is supported by in vivo studies with antibodies directed against ICAM-1 or LFA-1. In numerous models of transplant, including cardiac, bowel, islet and cornea, prolongation of graft survival was observed following treatment with anti-LFA-1, alone or in combination anti-ICAM-1 (see for example Nakakura E K et al., Transplantation 1993; 55(2):412-417). Anti-LFA-1 antibodies have also shown benefit in animal models of multiple sclerosis, lupus and inflammatory arthritis (see for example Kobayashi Y et al., Cell Immunol 1995; 164(2):295-305). The first LFA-1-targeted therapeutics to be tested clinically were anti-LFA-1 antibodies. Odulimomab showed efficacy in clinical trials of bone marrow transplant (Stoppa A M et al., Transpl Int 1991; 4(1):3-7) and in kidney transplant clinical trials (Hourmant M et al. Transplantation 1994; 58(3):377-380). The humanized anti-LFA-1 antibody Raptiva® (anti-CD11a, hu1124, efalizumab), marketed for psoriasis has provided the clinical proof of concept for the role of LFA-1 (Leonardi C L et al., J Am Acad Dermatol 2005; 52(3 Pt 1):425-433).
Thus, the prior art has demonstrated that large protein molecules which antagonize the binding of the ICAMs to the Leukointegrins have therapeutic potential in mitigating inflammatory and immunological responses often associated with the pathogenesis of many autoimmune or inflammatory diseases. However proteins have significant deficiencies as therapeutic agents, including the inability to be delivered orally and potential immunoreactivity which limits the utility of theses molecules for chronic administration. Furthermore, protein-based therapeutics are generally expensive to produce.
It follows that small molecules having the similar ability as large protein molecules to directly and selectively antagonize the binding of the ICAMs to the Leukointegrins would make preferable therapeutic agents.
Several small molecules have been described in the literature that affect the interaction of ICAMs and Leukointegrins. For example, U.S. Pat. No. 6,355,664 (and the corresponding WO 98/39303), 6,710,664, 6,977,267, 7,199,125 and WO 2006065908 disclose a class of small molecules, having a hydantoin core, that are inhibitors of the interaction of LFA-1 and ICAM-1. U.S. Pat. No. 6,492,408 (and corresponding WO 01/07440 A1), U.S. Pat. No. 6,844,360, U.S. Pat. No. 6,852,748, WO 2006/107941 and WO 2007/027233 all discloses compounds having this same activity that instead have a 6,7-dihydro-5H-imidazo[1,2-a]imidazole core. In addition, U.S. Pat. Nos. 6,673,825 and 6,974,815 and US Patent Application Publication 20060052434 disclose small molecules having a urazole, hexahydrobenzimidazole and pyrrolizine core respectively that are inhibitors of the interaction of LFA-1 and ICAM-1.